Why does long course always feel so long?

Lately I've been feeling fairly tired lately.. I just want to sleep all the time. I'm not sure what it is but I just have no energy. I went to my swim practice last night and it wasn't too bad. We started with a 200 backstroke and then a 4x100 kick with fins on 2:00. Then we had a choice of doing one of two sets. Either 5x200 (first 3 IM and the last 2 50 swim, 100 kick, 50 swim) on 4:00, or 3x800 on 15:00. Needless to say that pretty much everyone did the 5x200. The only person who did the 3x800 in our group was Kim. She's a bit of a distance person so I am sure she didn't mind... After we did the 5x200, we did 6x50 on 1:00 sprinting in and out of the wall which was tiring in itself. I mixed it up doing freestyle and backstroke. After that, we had a warm down which I did about 100m.

In any case, I just couldn't get going this practice... my stroke felt good but my energy level was really low. I was able to make all the intervals but not by much. Chris seems to be swimming well these days so I always let him go ahead of me.

I hope that I start feeling more energetic soon and maybe feel like I can get in better shape.. that way, long course won't feel so long anymore...